Question

You are building a FastMCP server that exposes a tool to retrieve interface statistics from network devices. Your team wants the AI agent to reliably pass a valid device hostname and an interface name, and you want FastMCP to automatically generate the tool's input schema so the LLM understands the expected parameters. Which approach correctly enables FastMCP to auto-generate the tool's JSON input schema for the agent?

Accepted Answer

Add Python type hints (e.g., hostname: str, interface: str) to the function parameters of the @mcp.tool()-decorated function so FastMCP infers the schema from annotations and docstring.

Answer

Serialize the parameters into a single JSON string argument and have the function parse it manually with json.loads() inside the tool body.

Answer

Define a global dictionary named INPUT_SCHEMA in the module and register it with mcp.set_schema() before starting the server.

Answer

Use **kwargs in the tool function signature so the agent can pass any arbitrary parameters without a fixed schema.